Your math doesn't make sence in real world. Either he run his 1070 at 100 or 150 wats PL, the hashrate for ETH will not increase, it will remain at 30-31 MH/s. So he is effectivly saving 50 watts per card while getting the same hashrate, what's wrong with that?
There is exactly 0 chance that you can cut the power consumption of
any electronic component and receive the exact same output. If you could, Bitmain would already have an S11 on the shelves that uses 1 watt. If my math fails to make sense to you, it's likely because you don't even math, bro.